Table of Contents
In this article, we will discuss the solution to Dampness on wet walls.
Dampness may be defined as a condition of being slightly wet. Dampness directly influences the strength of structure should dampness should be avoided.
1. Causes of Dampness
The causes of dampness are as follows:
a. Heavy Rain
If the exterior walls of the building are not covered then heavy rainwater may affect the building walls.
If the building is located in a region that cannot be smoothly drained off, dampness will affect the building.
These problems are raised due to bad workmanship in construction.
The recently constructed walls stay damp for a short time.
The very flat slope of a roof may also lead to the penetration of rainwater which is temporarily stored on the roof.
The parapet walls and compound walls should be provided with a damp proofing course on their exposed tops. Otherwise, the dampness entering through these exposed tops of such walls may lead to a serious result.
b. Ground Water Table
If the groundwater table is above, it will influence the foundation, because the construction material employed for the foundation soaks the water from the ground by capillary action.
2. Effects of Dampness
The effects of dampness are as follows:
a. The regular existence of moisture in the walls may induce efflorescence which may result in the disintegration of stone, bricks, tiles, etc.
b. The plaster will be softened and may crumble.
c. Electric fitting may affect.
d. Distempers or paints may damage.
e. Unhealthy conditions for occupants.
f. Growth of termites.
g. The steel utilized in building construction may be eroded.
h. Unattractive patches are formed on the wall surface and ceiling.
i. The material employed as a floor covering is extremely damaged.
A damp proof course is commonly abbreviated as the DPC.
It is a barrier or obstruction that is primarily designed to prevent moisture from rising by the capillary action.
The capillary action through which the moisture rises is known as rising damp.
In other words, a damp proof course can be defined as the layer of material that is used to prevent the penetration or passage of moisture inside the structure through the floors, walls, or roofs.
3. Damp Proofing Material
The damp-proofing materials used are as follows:
a. Mastic Asphalt/ Bitumen Asphalt
The mastic asphalt mainly consists of bitumen that is mixed with the fine sand in the hot state to form an impervious mass.
When the mixture is hot, the consistency is such that it allows the mixture to spread evenly to a depth of about 2.5cm to 5cm.
Upon cooling, the mixture sets.
However, special care must be taken while laying the mastic asphalt as the damp-proof course.
b. Hot Laid Bitumen
The hot-laid bitumen is mostly used on a bedding of cement concrete or mortar.
It is usually laid in two consecutive layers at the rate of 1.75kg/m² of the area.
c. Bitumen Felts (Sheets)
The bitumen felts consist of a 6mm thick sheet of bitumen prepared in rolls and having a width equal to that of a brick wall.
d. Metal Sheets
Metal Sheets are used throughout the thickness of the walls to prevent dampness.
Mostly, metal sheets of aluminum, lead, and copper are used for such purposes.
These sheets are coated with asphalt such that the thickness of the sheet is equal to or greater than 3mm.
The metal sheets of lead must be laid over the lime mortar instead of cement mortar because the chemical reaction between cement and lead may occur.
Metal sheets are highly effective in preventing dampness but are relatively expensive.
e. Rich Concrete
Rich Concrete is the most commonly used material in DPC.
Usually, rich concrete in the proportion 1:2:4 that is painted with two relative coats of hot bitumen is used for the horizontal damp proof course.
It is suitable for the portions of the building or structure that are not subjected to excessive damping. It prevents the ingress of moisture by the capillary action.
Mortar is extensively used for vertical damp-proof courses.
Usually, a 2cm thick rich cement layer and sand mortar(1:3) are applied on the inner surface of the external wall.
After laying the mortar, the surface is painted with hot bitumen in two coats.
Bricks are utilized when adequate damp proofing is required on a comparatively low budget.
Mostly, dense bricks and over-burnt bricks are used for this purpose.
The bricks are laid in rich cement and sand mortar of a ratio of 1:3.
It is used for the DPC in the cheap type of construction.
h. Stones and Slates
Two layers of stones are laid in lime, cement, and sand mortar (1 lime :1 cement: 6 sand) which acts as DPC.
In some cases, the slate and the stone slabs can also be laid in cement sand mortar.
It is mostly used where quality stones are found easily at a cheap rate.
4. Solution to Dampness on Wet Walls
The solution for dampness are as follows:
a. Enhance the drainage of the site. Ensure the nearby ground slopes away from the building.
b. Check there’s sufficient room under the floorboards for moisture to disappear from the soil beneath and pass out through sub-floor wall vents.
c. Establish a damp-proof course. This position is best left to the professionals.
Hope you got an idea of a Solution to Dampness on Wet Walls.
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